With regard to the conventional power supply pack structure, for example, Japanese Patent Laying-Open No. 2002-175791 discloses an interlock device for a secondary battery which aims at ensuring improved safety for operators and securing reliability of the relock operation by the operators. The interlock device disclosed in this document is provided in a case which houses a secondary battery and an apparatus for controlling the secondary battery.
The interlock device includes a safety plug which is attached to the case's lid for the secondary battery and a lock mechanism which locks the case's lid for the apparatus for control. The safety plug attached to the case's lid for the secondary battery allows the electric power of the secondary battery to be received. When the safety plug is removed, receipt of the electric power of the secondary battery is interrupted. The safety plug which is removed from the case's lid for the secondary battery is attached to the lock mechanism, to thereby unlock the lock mechanism and inhibit the disconnection of the plug from the lock mechanism. This configuration allows the operators to open the case's lid for the apparatus for control only in the state in which receipt of the electric power of the secondary battery is interrupted.
In contrast to the above-described battery pack structure, a service plug which permits and interrupts the receipt of the electric power of the secondary battery may be housed in the case, and an opening for accessing the service plug may be formed in the case. In this instance, when the secondary battery is required to be replaced during maintenance, the battery pack housing only the secondary battery is transported since the existing apparatus can be continued to be used. During the transportation, however, even if the case is configured not to open, there are possibilities that the cable of the secondary battery through which charge and discharge currents flow may be taken out from the opening and the terminal on the cable may be accidentally touched.